Chemical-Mechanical Polishing (CMP) slurries can be used to planarize metal layers. Such CMP slurries can include a buffered solution, an oxidizer, and an abrasive. The oxidizer chemically passivates or oxidizes the metal, and the abrasive physically polishes or removes the oxidized metal, which is softer than the unoxidized metal. CMP slurries for polishing tungsten metals require precise quantities of the oxidizer, which has an extremely short useful lifetime. Therefore, the new quantities of the oxidizer must be added to the CMP slurry to maintain the necessary chemical activity.
Prior techniques for determining when additional amounts of oxidizer are required include manual techniques such as titration. Typically, these manual techniques require at least a quarter of an hour to complete before the appropriate amount of oxidizer to be added to the CMP slurry is determined. This long delay between the sampling of the CMP slurry and the addition of the oxidizer to the CMP slurry produces poor manufacturing process control.
The short useful lifetime of some CMP slurries also produces other problems in existing CMP systems. For example, many CMP systems use large day tanks that hold significant quantities of CMP slurry to be used during an entire day or at least during an eight hour manufacturing shift. These day tanks consume large amounts of floor space and are expensive. Furthermore, large amounts of oxidizer must be added periodically to several types of CMP slurry stored in day tanks. Moreover, a new batch of CMP slurry may have a residence time or dwell time before the CMP slurry can be used or beyond which the CMP slurry may not be used. Therefore, the large quantities of CMP slurry in the day tanks may have residence time problems as new batches of slurry are introduced to the day tank and/or as older slurry ages beyond its useful life and must be rejuvenated via chemical additions.
Accordingly, a need exists for a method of manufacturing semiconductor components that includes a process for easily, accurately, and cost-effectively detecting and controlling a concentration of a component in a mixture. As applied to CMP processing, a need exists for a CMP system that can easily, accurately, and cost-effectively detect and control a concentration of an oxidizer or other time-sensitive chemical components in a CMP slurry.